DP Chemistry (last assessment 2024)

Test builder »

Question 19N.3.sl.TZ0.13b

Select a Test
Date November 2019 Marks available [Maximum mark: 2] Reference code 19N.3.sl.TZ0.13b
Level sl Paper 3 Time zone TZ0
Command term Calculate Question number b Adapted from N/A
b.
[Maximum mark: 2]
19N.3.sl.TZ0.13b

Red supergiant stars contain carbon-12 formed by the fusion of helium-4 nuclei with beryllium-8 nuclei.

Mass of a helium-4 nucleus = 4.002602 amu
Mass of a beryllium-8 nucleus = 8.005305 amu
Mass of a carbon-12 nucleus = 12.000000 amu

(b)

Beryllium-8 is a radioactive isotope with a half-life of 6.70 × 10−17 s.

Calculate the mass of beryllium-8 remaining after 2.01 × 10−16 s from a sample initially containing 4.00 g of beryllium-8.

[2]

Markscheme

ALTERNATIVE 1
3 half-lives ✔
0.500 g «of beryllium-8 remain» ✔

 

ALTERNATIVE 2
m = 4.00 ( 1 2 ) 2.01 × 10 − 16 6.70 × 10 − 17 ✔
0.500 g «of beryllium-8 remain» ✔

 

ALTERNATIVE 3
λ = «  ln ⁡ 2 6.70 × 10 − 17 »= 1.03 × 1016 «s−1» ✔
m = «  4.00   e − 1.03 × 10 16 × 2.01 × 10 − 16  =  » 0.500 «g» ✔

 

NOTE: Award [2] for correct final answer.

Syllabus sections